An Apple a day could not keep the police away
The accessory makers accurately guessed the changes that were made to the iPad 2. The newly added rear-facing camera, larger speaker grill and the thinner frame were all present in the cases which showed up all over the internet in late December, 2010. Even the integrated microphone and its placement was predicted by the manufacturers.
Apple has been known to be very secretive about its products; it maintains a vice-grip on even the smallest of details, whether it be a refresh on its range of computers or an update for its iOS software. Even the lastest refresh rumour for the iMacs has no real information, everything is based on speculation.